This invention relates generally to an ink-jet type recording apparatus for ejecting ink droplets onto a recording medium, and more particularly, to a structure of an ink tank cartridge for use in a ink-jet type recording apparatus.
In a conventional recording apparatus, ink is supplied to a recording head from an ink tank constructed as a cartridge. The benefits of using an ink cartridge serving as an ink tank is that ink does not smear due to the leakage of ink while refilling new ink or the like. However, undesired air bubbles easily enter the ink tank which cause problems such as an ink failure.
In order to prevent air bubbles from entering the ink tank, several techniques have been proposed. For example, Unexamined Japanese Patent Application (OPI) No. Hei. 3-92356 discloses an ink-jet recording apparatus in which an ink supply port is disposed below an ink tank. The tank is formed with a rubber tap and a metal ink supply needle which penetrates through the rubber tap to form an ink flow path that communicates with ink nozzles of the recording head. To easily penetrate through the rubber tap, the ink supply needle is provided with ink supply holes on a side surface thereof. The supply holes have a diameter about 1 mm. The needle is constructed from a metal pipe formed of an anti-corrosion material such as stainless steel. Moreover, the tip of the pipe is extremely sharp to penetrate the rubber tap. Accordingly, the user must operate the sharpened needle very carefully or be subjected to potential injury.
To overcome the above problem, Unexamined Japanese Patent Application (OPI) No. Sho. 50-074341 proposes a solution. In this arrangement, a packing member is provided with a throughhole positioned at an end opening of an ink supply port. The throughhole of the packing member is sealed by a sealing member. Based thereon, the ink supply needle does not require an extremely sharp tip, since it is penetrating a seal member and not a rubber tap as in the prior art. However, in a conventional ink-jet recording apparatus using an ink tank which stores liquid ink directly therein, the apparatus suffers from several problems such as leakage of ink or a pressure difference which is due to an increase in pressure while penetrating the ink supply needle.
Furthermore, it is preferable to keep the ink supply pressure as a negative pressure from the ink tank to the recording head within a range from -30 to -100 mmAq (waterhead) to achieve a stable ink ejection of the recording head of the ink-jet type recording apparatus. However, due to the height level at which the ink tank is installed, it is difficult to control the ink supply pressure. This is particularly true when the ink-jet recording apparatus is configured with a carriage type system wherein a recording head and an ink tank cartridge are mounted on the carriage. Unexamined Japanese Patent Application (OPI) No. Hei. 2-187364 proposes that a porous member be housed within an ink tank (cartridge) to thereby generate a negative pressure between the ink tank and the recording head due to the capillary action of the porous member.
Japanese Patent Application Hei. 2-187364 is directed to one type of recording apparatus by which both an ink tank and a recording head are unitarily formed. When the ink contained in the ink tank is emptied, both of these components are replaced. Moreover, this application is silent with respect to the other problems or difficulties such as undesired air flow to the recording head or leakage of ink which may occur when the ink tank is selectively removed from the head.
Japanese Patent No. Hei. 3-61592 suggests 20 Torr as an appropriate negative pressure level for packing the ink tank cartridge. This negative pressure is much greater than the negative pressure under which the ink is filled within the tank. In fact, the negative pressure may cause a problem, because the ink tank cartridge may have atmospheric pressure previously applied thereto during the manufacturing process and because of the necessity of moving a filled cartridge some distance to the packaging station. Moreover, the timing for the ink-filling process and that for the packaging process are usually spaced far from each other. Therefore, air penetrating into the ink may be freed and produce air bubbles when a negative pressure applied during the packaging process is greater than that for the ink-filling process. As a result thereof, an undesirable ink-leakage may occur. Further, air bubbles generated in the porous member may obstruct the ink flowing from the ink tank cartridge to the recording head which could cause an ink-failure during the printing operation.
Accordingly, it is desirable to provide an ink tank cartridge in an ink-jet type recording apparatus which does not require a sharpened needle, is capable of preventing air (gas) from entering the ink supply path of the recording apparatus body even when the ink tank is replaced from the ink supply needle and has a high air tightness between the ink supply needle and the ink tank.